The Photohelic® Dwyer A3000 Switch-Gages function as versatile, highly repeatable pressure switches combined with a precise pressure gage employing the time-proven Magnehelic® gage design and measures and controls positive, negative or differential pressures of air and compatible gases.
There are Standard models are rated to 25 psig (1.7 bar) with options to 35 (2.4) or 80 (5.5 bar) psig.
The Single pressure 36000S models measure to 6000 psig (413 bar) with a 9000 psig (620 bar) rating. Only Two photo transistor actuated, DPDT relays are included for low/high limit control.
How Easy to adjust set point indicators are controlled by knobs located on the gage face.
There is Individual set point deadband is one pointer width - less than 1% of full scale.
And Set points can be interlocked to provide variable deadband - ideal for control of fans, dampers, etc.
Even during loss of electrical, Gage reading is continuous and unaffected by switch operation, power. You can Choose from full scale pressure ranges from a low 0-.25" (0-6 mm) w.c.until up to 30 psi (21 bar); single positive pressure to 6000 psig (413 bar).

Photohelic Sensing - How It Works

These typical applications, Dwyer A3000 Photohelic® switch/gages control between high and low pressure set points.
When pressure has changes, reaching either set point pressure, the infrared light to the limiting phototransistor is cut off by the helix-driven light shutter.
Resulting of phototransistor signal is electronically amplified to actuate its DPDT slave relay and switching occurs.
Dead band of between make and break is 1% of full scale or less - just enough to assure positive, chatter-free operation.